The present invention generally relates to liquid developing heads, liquid developing units and image forming apparatuses, and more particularly to a liquid developing head and a liquid developing unit used in an electrophotography type printer which is provided with a photoconductive drum and to an image forming apparatus having such a liquid developing head and liquid developing unit.
The developing unit used in the electrophotography type printer which is provided with the photoconductive drum may be categorized into a dry type developing unit which uses a toner in the powder form, and a liquid developing unit which uses a developing liquid. The grain diameter of the powder toner is on the order of 5 to 10 .mu.m, while the grain diameter of the toner within the developing liquid is on the order of 0.1 to 3 .mu.m and small. Accordingly, when the liquid developing unit is used, it is possible to carry out the printing with a high resolution as compared to the case where the dry type developing unit is used. In addition, compared to the case where the dry type developing unit is used, it is possible to obtain a high color reproducibility of the toner when the liquid developing unit is used, and the liquid developing unit is suited for carrying out the printing with a high picture quality.
On the other hand, there are demands to reduce the size of the electrophotography type printer. In order to meet such demands, it is desirable that the set up location and the set up position of the liquid developing unit can be selected with a large degree of freedom.
A conventional liquid developing unit 10 has a construction shown in FIG. 1. As shown in FIG. 1, a developing roller 14 and a squeeze roller 15 are arranged side by side above a tank 12 which stores a developing liquid 11. The developing roller 14 supplies the developing liquid 11 on a surface of a photoconductive drum 13, and the squeeze roller 15 removes the developing liquid 11 adhered on the surface of the photoconductive drum 13.
With respect to the photoconductive drum 13, the position of the conventional liquid developing unit 10 is generally limited to a position under the photoconductive drum 13 so that the developing liquid 11 will not leak. In other words, the degree of freedom of the set up location and the set up position of the conventional liquid developing unit 10 was poor.
For this reason, in the electrophotography type printer which can carry out a color printing, a yellow (Y) liquid developing unit, a magenta (M) liquid developing unit, a cyan (C) liquid developing unit and a black (Bk) liquid developing unit are provided sequentially below the photoconductive drum as proposed in a Japanese Laid-Open Patent Application No.5-273861, for example. In this proposed electrophotography type printer, a liquid developing unit moving mechanism successively shifts each of the liquid developing units to a position immediately below the photoconductive drum. As a result, it was difficult to reduce the size of the electrophotography type printer.